The first meteorological report of two brown dwarfs – celestial bodies larger than planets but smaller than stars – closest to us has just been produced.
The climate there is inclement, to say the least: incredibly hot, with a toxic cocktail roaming the atmosphere, and clouds of silicate particles akin to Saharan sandstorms.
Researchers used the James Webb Space Telescope’s recordings to conduct a detailed survey of atmospheric conditions on brown dwarfs, specifically a pair that orbit about six light-years from Earth, a measurement considered close on a cosmic scale. A light-year is the distance it takes light to travel in one year, or 9.5 trillion kilometers.
The information collected by Webb provides a three-dimensional view of how the weather changes during the brown dwarf’s rotation – the larger of the two taking seven hours and the smaller five – with multiple cloud layers found at different atmospheric depths.
The atmospheres of both brown dwarfs are dominated by hydrogen and helium, with small amounts of water vapor, methane and carbon monoxide. The temperature in their clouds reaches a maximum of 925 °C, a value similar to that of a common candle flame.
“In this study, we have created the most detailed weather map of any brown dwarf ever seen,” said astronomer Beth Biller of the University of Edinburgh’s Institute of Astronomy, lead author of the study published on Monday (15) in the academic journal Monthly Notices of the Royal Astronomical Society.
Brown dwarfs are neither stars nor planets, but something in between. They emit their own light because of how hot they are, “just like you can see coal turning red because of how hot it is,” Biller said. It’s this light that the researchers investigated with Webb. Unlike stars, brown dwarfs do not have nuclear fusion in their cores.
“Like planets, but unlike stars, brown dwarfs also have clouds that are made of precipitates in their atmospheres. It turns out that, although there are water clouds on Earth, the clouds of brown dwarfs are much hotter and probably made of hot silicate particles, something like a very hot Saharan sandstorm,” Biller said.
The current scientific consensus is that brown dwarfs formed from large clouds of gas and dust like stars, but they do not have enough mass to undergo nuclear fusion. Their composition is similar to that of giant gas planets like Jupiter, the largest in our solar system. Their mass is up to 80 times greater than that of Jupiter. For comparison, the mass of the sun is about 1,000 times greater than that of Jupiter.
The two brown dwarfs analyzed by Webb formed about 500 million years ago. Each is comparable in diameter to Jupiter, but one is 35 times larger than Jupiter and the other is 30 times larger.
Brown dwarfs are relatively common. About 1,000 are known, compared to more than 5,000 exoplanets. Webb primarily examines the cosmos using infrared light, while its predecessor, the Hubble Space Telescope, analyzed optical and ultraviolet light.
“The atmospheres of brown dwarfs are highly complex. Webb provides a huge leap forward in our ability to understand them by providing unprecedented sensitivity and wavelength range,” said astronomer and study co-author Johanna Vos of Trinity College, Dublin, Ireland.
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Source: CNN Brasil
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